1. Field of the Invention
This invention relates generally to switches for use with computer keyboards, and relates more particularly to a multipurpose keyswitch for controlling cursor movement on a CRT display.
2. Description of the Prior Art
A computer operator typically interacts with a computer through an input device such as a keyboard and an output device such as a cathode ray tube (CRT) display. The operator often must position a cursor on the CRT display via command inputs entered through the keyboard. Since cursor positioning may be required at any location on the CRT, means for both vertical and horizontal movement of the cursor must be provided.
One prior approach to cursor positioning used special function keys that were used solely for controlling cursor movement. Four of such keys were required to provide up and down cursor movement in the vertical direction and left and right cursor movement in the horizontal direction. One disadvantage to this approach was that the operator had to move his fingers from the home position in order to use the special function keys. Another disadvantage was that the keyboards had to be larger in size to accomodate four additional keys.
Another prior approach to cursor positioning was to use four of the existing alphanumeric keys as cursor control keys to provide the four directions of cursor movement. To distinguish cursor movement operation of a cursor control key from its normal character entry operation, an additional key, such as the CONTROL key, had to be depressed in combination with the cursor control key. While this approach overcame some of the disadvantages of the special function keys, it has been found that operators were slow to learn this approach due to confusion as to which cursor control key provided which cursor movement.
Still another prior approach to cursor positioning was to use a separate graphic interaction device, such as a mouse, data tablet, or joystick. One disadvantage to this approach was that additional keyboard space was required for mounting a joystick, and additional desk space was required for peripheral devices such as a data tablet or a mouse. In addition, the operator had to move his hand from the keyboard to the device and had to use major muscle movement to operate the device.